The present invention relates generally to expandable, intraluminal vascular grafts, generally referred to as stents. More particularly, the present invention relates to a balloon expandable, crush resistant locking stent.
Expandable intraluminal vascular grafts, generally called stents, are adapted to be implanted into a patient's body lumen, such as a blood vessel, to maintain the patency of the vessel. These devices are frequently used in the treatment of atherosclerotic stenosis in blood vessels, especially after percutaneous transluininal coronary angioplasty (PTCA) procedures, to reduce the likelihood of restenosis of a blood vessel.
In expandable stents that are delivered with expandable catheters, such as a balloon catheter, the stents are positioned over the balloon portion of the catheter and expanded from a reduced diameter to an enlarged diameter greater than or equal to the artery wall, by inflating the balloon. Stents of this type can be expanded and held in the enlarged diameter by deformation of the stent as taught in, for example, U.S. Pat. No. 4,733,665 to Palmaz; by engagement of the stent walls with respect to one another as in, for example, U.S. Pat. Nos. 4,740,207 to Kreamer, 4,877,030 to Beck et al., and 5,007,926 to Derbyshire; and by one-way engagement of the stent walls together with endothelial growth into the stent as shown in U.S. Pat. No. 5,059,211 to Stack et al.
A number of conventional stents in order to be easily expandable have a rolled up cylinder construction. For example, U.S. Pat. No. 5,443,500 to Sigwart discloses an intravascular stent intended for implantation in a stenotic area or zone of obstruction of a blood vessel consisting of a flat sheet that is perforated to form a reticulated or lattice type structure with undeformable links and made of malleable material. The sheet is temporarily rolled up and locked in a spiral with a relatively small diameter on a deflated balloon mounted on the end of a catheter and is held in the rolled up state by a tie laced into overlapping links. Once the device is in place in the restricted area of the blood vessel to be treated and after the tie is removed, the rolled sheet is expanded to a desired diameter by inflating the balloon.
U.S. Pat. No. 5,423,885 to Williams discloses an expandable, balloon catheter delivered intravascular stent having a plurality of protrusions on its outer surface for engaging the artery walls in which it is disposed. The stent has a rolled up sheet construction, wherein apertures are formed in the stent body from the space vacated in the body by the material forming the protrusions. When the stent is expanded by the balloon catheter, the protrusions engage both the apertures and the artery walls to lock the stent into the expanded diameter.
U.S. Pat. No. 5,306,286 to Stack et al. discloses an expandable stent having a rolled up mesh construction. The stent can be reduced in diameter by a rolling motion while still having a cylindrical configuration on its outer surface for uniform engagement with a vessel wall. The rolled up, absorbable stent is mounted on either a balloon catheter, a mechanically expandable catheter, or other suitable stent delivery assembly. By expanding the distal balloon of the catheter or mechanically expandable distal end portion of the mechanically expandable catheter, the stent is expanded so as to engage the vessel wall.
U.S. Pat. No. 5,192,307 to Wall discloses a stent-like prosthesis which is formed of plastic or sheet metal and is expandable or contractible for placement. The stent may selectively be biased towards a closed position and lockable in an open position or biased in an open position and lockable in a closed position. In the former case, the stent is put into place in its collapsed condition, then forcibly expanded by a balloon to the desired locked condition. In the latter case, the stent may be held by a pin or the like in its collapsed condition, and the pin removed to allow the stent to assume its open position. The locking function is performed by one or more hooks formed into the wall which engage complementary recesses formed in an opposing wall to mechanically interlock the rolled up sheet forming the stent.
U.S. Pat. No. 5,441,515 to Khosravi et al. discloses an intravascular stent comprising a cylindrical sheet having overlapping edges that interlock. The edges having a series of protrusions and apertures that interlock and ratchet as the stent expands to an open position to support a section of arterial wall. The stent may be expanded by a balloon catheter or it may be self-expanding. A plurality of retaining members keep the stent open, and a buckle fastening member is used in one embodiment.
Copending U.S. Ser. No. 08/512,300, filed Aug. 8, 1995, entitled "Ratcheling Stent," is a divisional application of U.S. Pat. No. 5,441,515 to Khosravi, relating to a ratcheting stent having a rolled, cylindrical sheet construction.
There is, however, still a need for an expandable, crush resistant locking stent that has a durable, crush proof construction with a simplified locking mechanism. The crush proof aspect of the stent minimizes the possibility of an embolism in the vessel if, after implantation, the stent collapses as a result of, for example, an accidental chest trauma or impact on a vessel close to the skin such as the carotid arteries.